Chiral charge pumping in graphene deposited on a magnetic insulator

Abstract

We demonstrate experimentally that a sizable chiral charge pumping can be achieved at room temperature in graphene/Yttrium Iron Garnet (YIG) bilayer systems. The effect, which cannot be attributed to the ordinary spin pumping, reveals itself in the creation of a dc electric field/voltage in graphene as a response to the dynamic magnetic excitations (spin waves) in an adjacent out-of-plane magnetized YIG film. We show that the induced voltage changes its sign when the orientation of the static magnetization is reversed, clearly indicating the broken mirror reflection symmetry about the planes normal to the graphene/YIG interface. The strength of effect shows a non-monotonous dependence on the spin-wave frequency, in agreement with the proposed theoretical model.

Direct detection of induced magnetic moment and efficient spin-to-charge conversion in graphene/ferromagnetic structures

“…Recent experimental studies have shown that YIG turned out to be an ideal ferromagnetic insulating (FMI) material to induce spin properties in hybrid structures with single-layer graphene (SLG) 38,[55][56][57][58][59] . Among other reasons for the use of YIG, we can mention its excellent mechanical and structural properties, as well as its extraordinary low magnetic damping.…”

Terahertz response of gadolinium gallium garnet (GGG) and gadolinium scandium gallium garnet (SGGG)

“…Recently, strain induced out-of-plane ferrimagnetic ordering in TIG films grown on (S)GGG substrates has been utilized to generate room-temperature magnetic proximity effects in topological insulators [20]. Similar XIG/GGG heterostruc- * sabbagh2@uwm.edu † george@uwm.edu ‡ weinert@uwm.edu § fan.shi@mail.wvu.edu ¶ cheng.cen@wvu.edu tures have also been used to realize spin pumping in singlelayer graphene [42,43]. Garnets, with the highest magneto-optical Verdet constants in bulk media, are the most common materials for Faraday rotators and optical isolators at visible wavelengths [44][45][46].…”

“…For example, alternating deposition of ultra-thin XIG and GGG films has led to the realization of all-garnet magnetooptical photonic crystals (MOPCs) [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61]. Additionally, heterostructures combining (S)GGG-based garnet substrates and 2D quantum materials that exhibit giant Faraday rotations at THz frequencies [20,42,43] can potentially lead to broadband magneto-optical devices that cover the whole THz-tovisible frequency range.…”

Magnon-driven chiral charge and spin pumping and electron-magnon scattering from time-dependent quantum transport combined with classical atomistic spin dynamics

“…The SWs can be excited in equilibrium as incoherent thermal fluctuations, which then reduce the total magnetization with increasing temperature. They can also be excited by external fields [6,[8][9][10][11][12] which leads to coherent propagation of SWs as a dispersive signal. The electron-magnon interaction can provide a glue for Copper pairs in magnon-mediated superconductivity [13][14][15][16].…”

“…On the other hand, experiments [6,[8][9][10] exciting dipole or exchange dominated SWs are commonly interpreted using classical micromagnetics simulations [4]. In such a picture, SW is described by trajectories of classical vectors M i (t) of fixed (unit) length, pointing along the direction of localized magnetic moments, which precesses whose localized magnetic moments precess as coherent SW mode [46] with k = 0 in Eq.…”